This invention relates to endless power transmission belts.
Endless power transmission belts having a cross-section in the form of a trapezoid, and commonly known as V-belts, are well known and widely used. V-belts transmit power by wedgingly engaging the complimentarily shaped groove of a V-pulley. The forced contact between the sides of the pulley groove resists slippage of the belt in the pulley. It is desirable, however, for the belt to enter and leave the pulley with as little resistance as possible. It has been found that a high coefficient of friction between the belt and the pulley results in a comparatively high belt operating tension, while a reduced belt to pulley coefficient of friction results in a reduced belt operating tension.
V-belts are normally characterized by such basic elements as a load-carrying section, generally composed of strength cords embedded in an elastomer, an upper tension section and a lower compression section. An example of a belt of this type is described and illustrated (FIG. 1) in U.S. Pat. No. 3,863,516. The belt may be covered by a fabric envelope or cover having an elastomer on one or both surfaces thereof, as described and illustrated (FIG. 2) in U.S. Pat. No. 3,863,516. The fabric covered belt is known in the art as a wrapped, molded V-belt. Where a fabric cover is not used, the resulting belt is commonly known as a molded or raw-edge belt, depending upon the particular manufacturing method employed.
The coefficient of friction of raw-edge belts can be reduced by incorporating graphite into the elastomeric material which makes up at least one of the load-carrying, tension and/or compression sections of the belt, as described, for example in U.S. Pat. Nos. 4,024,773 and 4,031,768. In the case of fabric covered V-belts polyfluorohydrocarbon resins which have polymer lubricating properties may be incorporated into the elastomeric material which is used to impregnate the cover fabric, as described in U.S. Pat. No. 3,661,823.
It is an object of the present invention to provide a novel method for reducing the coefficient of friction between a metal pulley and a wrapped, molded V-belt.
It is another object of this invention to provide a novel wrapping, molded V-belt having reduced coefficient of friction pulley-contacting sides.
It is a further object of this invention to provide a method for manufacturing a wrapped, molded V-belt having reduced coefficient of friction sides.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art from the following description of the invention.